Evaluate a function with variable number of parameters.

eval_fun.py

def eval_fun(f, **args):
    """ (str, dict) -> object
    f: Function as string.
    args: dictionary with arbitrary variables.
    Use arbitrary args in **args to eval general functions.
    Examples:
    >> eval_fun('x**2',x=5)
    25
    >> eval_fun('x*y', x=3, y=2)
    6
    """
    for key in args.keys():
        exec(str(key)+'='+str(args[key]))
    return eval(f)
    
    
if __name__=="__main__":
    import doctest
    doctest.testmod(verbose=True)